As I supported the request for more build threads thru a previous post, I am adding the build of my 6" Ruston Proctor Steam Traction Engine.

Even though the model is a half size scale model of the original, it is only a medium size engine. The original engine weighed 3 1/2 tons and the model will weigh about 650 kg. It has a 10" dia boiler and the rear wheels are 24" diameter. Small enough to transport is a standard 6' x 4' box trailer.

A set of drawings and castings was obtained from Live Steam Models and shipped by sea freight to Sydney, Australia.

The drawings for the model engine were drawn with imperial dimensions and specified inch size plates and pipe, many of which were not available. The biggest change that I had to make was making the boiler. The drawing specified a barrel of 10" OD (254mm) but this size is not available in commercial pipe, unless you rolled a special tube. I decided to use10" NB pressure pipe (273mm OD) but this meant changing the width of the engine. The distance over the horn plate was now wider which effected the width of the rear axle and most of the components.

Because of all these changes and some mistakes and missing dimensions, I re-drew all parts of the engine using Solidworks CAD software and created my own set of detail drawings.

I had worked for most of my working life as a mechanical engineering draftsman but have had little experience actually running a mill and a lathe and was advised by a toolmaker to start with the front wheels as they were a good introduction to the different machining techniques.

Milling the slots in the front wheel hubs for the spokes.

To bend the wheel spokes, I used a press which I converted from a 12 tonne pipe bender and machined an angled plate to press against.

Home Made 12 Tone Press

The angle base plate for pressing bend in spokes required a little trial and error to achieve the correct angle to overcome the spring-back in the spoke angle when the press was released. This arrangement produced a consistent bend angle in all of the spokes.

The holes in the spokes being stack drilled for the rivets which attach them to the wheel rim.

Wheel assembly mounted on a temporary axle which is bolted to the mill table. All spokes assembled in the wheel hub and the wheel ring centered about the axle and mounting holes drilled.

I did not have an accurate way to measure the bore for the wheel hub, only an outside micrometer, so made a Go/NoGo plug gauge. Then used the plug gauge to transfer the diameter to the bush. With the dial indicator I could machine the bush slightly bigger for a press fit.

The plug gauge became a universal tool for measuring and was also used as the axle which I used to assemble and drill the spokes on the mill. (shown in previous photo).

Pressing bronze bush into wheel hub

CONSTRUCTION of REAR WHEELS

The rear wheels which are similar in construction to the front wheels but larger and more complex. The wheels are 24" diameter x 5 inches wide. The LH hub can be disconnected from the drive gears and free-wheel by removing 2 pins. A rope winch can then be engaged to haul objects while the engine is stationary.

I do not have a set of rolls to make the wheel rims so so paid for them to be supplied. The spokes were laser cut and I gave a CAD drawing to the laser company in .dxf format. They were supplied within 0.2mm of the required size and only needed a slight lick with a linisher to finish.

The RH fixed hub was mounted on a rotary table and is located on center by a specially turned bush which fits the hole in the table and the bore of the hub. The mill head was then centered on the bore.

The position for the slots was then marked out on the top surface by painting with a black "Texta" pen and scribing their outline with a sharp pointer held in the mill chuck. Slots were then cut.

Holes for attaching spokes drilled, then tapped, using the mill to guide the tap and keep it vertical.

The mill table was moved from the datum center position to drill bolt holes and countersink. Rotary table indexed to drill the next hole.

Drilling, tapping and counterboring holes in the left hand (free wheeling) hub

Machining the cover for the LH rear wheel hub on my 9" Southbend lathe.

Assembly and machining of attachment holes for LH rear wheel hub.

Laser cut, rear wheel spokes being drilled in a simple jig on the mill table The positions for the holes was stored in the DRO , allowing for quick repeated drilling of all spokes.

Final assembly and drilling of holes to attach the spokes to the ring on the RH rear wheel.

Final assembly and drilling of holes to attach the spokes to the ring on the LH rear wheel. The spokes are attached with temporary bolts which will be replaced by 1/4" dia round head rivets.

This was then welded to the outer wheel rim and the fillet weld ground to produce a smooth fillet. When painted it should look like a fillet in a cast wheel. The

Hi Neil,

Someone asked for build threads and foolishly I put my hand up and did not realize how much work was involved but I will keep it coming. Lots more yet.

Paul

CRANKSHAFT BEARING HOUSING and ADJUSTABLE BRONZE BUSH

The crankshaft is supported by 2 bearing assemblies, one on each side. The bronze bushes are split into 3 parts and are adjusted for the fit with the crankshaft by replacing shims, Alignment of the shaft (forwards and back) is also adjusted by shims.

Crankshaft bearing assembly (alignment shims not shown)

Machining of the crankshaft bearing housing

The housing was a difficult shape to hold in the lathe, so I made a temporary plate which was bolted to 2 of the mounting holes and held it by a 4 jaw chuck. Then turned the location diameters which fit into matching holes in the engine horn plates.

The sides of the supplied bronze casting for the bush was milled to square it up, Then painted with a black Texta pen and the position for saw cuts marked out with the aid a scriber in the mill.

First saw cut thru both sides.

Second saw cuts

The sawn faces of the cut bush pieces being milled smooth

I made a temporary heating hearth out of aerorated concrete blocks and joined the bush together with soft solder. The solder will be melted and the bush separated after final machining.

Final machining of the bronze bush assembly,

FLYWHEEL

The flywheel is 15" diameter x 2" wide and was supplied as a casting. Again, I had to use a mates lathe as it was too big for my little Southbend.

I used the inside lip on the flywheel to hold it in a 4-jaw chuck. The lip was small and slightly tapered, so cut a center hole and used the tail stock while turning the outside and the side of the boss in case it came loose. Then drilled a hole thru the casting and bored the hole to the correct size.

The crown on the outside edge was formed by cutting a slight taper on each edge, then blending it into a radius. The flywheel then rotated and held by the boss to machine the other side.

TESTING VALVE SEALS & SETTING RELEASE PRESSURE

The pressure relief valve attached to a testing plate for checking for leaks with the valve inserts and for doing a preliminary release pressure setting. Each valve can be checked individually.

Note: these tests can be done with compressed air but the final setting must be done on the engine with steam.

The test plate has an “O”-ring that seals against the underside of the valve, allowing each side to be tested independently.

The test plate can also be used to blank off the steam chest when the boiler is being tested.

Note: This test must be done by pumping water into the boiler. Air within the boiler must be purged before pressurizing the boiler because air is an expandable medium and if the boiler fails, could explode. Water does not compress (well not much) and if the boiler fails under pressure does not explode.